Lighting unit



Jan. 21, 1969 w. a. ELMER 3,423,582

LIGHTING UNIT Filed Jan. 5, 1967 FIG.2

B b o A FIGA FIG.3

WILLIAM B. ELMER INVENTOR BYM 6 ATTORNEY United States Patent O ClaimsABSTRACT OF THE DISCLOSURE A reflector for producing a generallyrectangular beam for illuminating an area for taking photographs. Thereflector is composed of four parabolic quadrants, each with a somewhatdifferent axis, so that each produces a beam in a quadrant of arectangle that it is desired to illuminate, the reflector surface beingdimpled and the filament large enough to be only vaguely focussed, inorder to smooth out the light into a single rectangle. The quadrants areas it cut from a paraboloid of revolution, the vertical cuts being madein a plane passing through the focal point at a 4 /2 angle, thehorizontal at a 3%, angle. The commercial reflector is stamped from asingle piece of sheet metal.

BACKGROUND OF THE INVENTION Field of invention The invention relates toequipment for producing a beam of light. Such equipment generallyincludes a lamp and reflector. The present application is directedparticularly to equipment having a lamp of the tungsten filament type ina quartz envelope containing a halogen vapor, usually iodine or bromine.Such lamps are now generally called tungsten halogen lamps. Theinvention is especially directed to the combination of such lamps with areflector giving a generally rectangular beam, useful in illuminating anarea for photography.

Description of the prior art The prior devices in the field generallyused beams of circular cross-section, which can be produced simply. US.patent application Ser. No. 414,073 filed Nov. 27, 1964 and now U.S.Patent No. 3,331,960, dated July 18, 1967 by the applicant taught theproduction of a rectangular beam by overlapping the beams from fourseparate parts of a reflector, the curvature of the parts diverging fromthe parabola.

SUMMARY OF THE INVENTION The applicant has discovered that a generallyrectangular beam can be produced by using four approximate quadrants ofthe same parabola, each being tipped toward the axis of the resultantpiece, so that the light from each quadrant crosses the reflector axisand illuminates a quadrant of a rectangle at a distance from thereflector, the filament being large enough so that the image of thefilament on the rectangular field to be illuminated will not produceappreciable non-uniformity in the beam. The reflector surface can beetched or peened to diffuse the image further.

In practice, a paraboloid of revolution can be formed from sheet metal,and if set with its main axis horizontal, one quadrant can be cut fromit by cutting in two planes transverse to each other, for example, onenearly horizontal and one nearly vertical. The horizontal cut is made ina plane passing through the focal point of the paraboloid at smallangle, say about 3 /2 to the horizontal and directed downwardl towardthe rear of the reflector. The other cut is made in a plane at a smallangle, say about 4 /2 to the vertical, directed toward the quad-3,423,582 Patented Jan. 21, 1969 ICC rant to be cut, and passing throughthe focal point. Quadrants cut in this manner are placed opposite eachother on opposite sides of the axis of the assembled reflector, andanother type of quadrant, in which the 4V2 cut is made on the other sideof the vertical and the 3 /2 cut made on the other side of thehorizontal, are used as the intermediate quadrants. The final reflectorwill generally be made in one piece, with each quadrant being the samein size, shape and position as if made up of four separate quadrantsjoined together.

BRIEF DESCRIPTION OF DRAWINGS In the drawings, FIG. 1 is a general viewof the finished device; FIGURE 2 is a schematic diagram of how the cutsare taken; FIGURE 3 is a view of the open end of the reflector; andFIGURE 4 is a view of the rectanglar field illuminated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGURE 1, the reflector 1has a hole 2 at its apex through which the lamp 3 extends into theconcave front of said reflector 1. The lamp 3 has the envelope 4 withthe coiled-coil filament 5 transverse to the axis of the reflector, andsupported in the envelope 4 by lead-in Wires, in the usual manner, notshown. The envelope 4 has a base of the usual type (not shown) insidesocket 6, into which it fits and is held.

The reflector 1, although in a single metal piece, is made up of fourquadrants. The quadrants can be considered as being cut from aparaboloid of revolution 7 as in FIGURE 2. Quadrant A is cut by oneplane passing through the focal point P of the paraboloid 7 at adihedral angle C of about 3 /2 to a plane passing through the axis 8,and by another plane 9 making an angle D of about 4 /2" with a plane atright angles to the plane through the axis 8. That is if the angle of 3/2" is to a horizontal plane, the angle of 4 /2 would be to a verticalplane.

This makes one quadrant A, and in FIGURE 3, showing a front view of thereflector 1, this quadrant A is used in the two opposite but contiguouspositions shown, with a quadrant B intermediate each of the quadrants Aand joined to them to form an integral unit.

The quadrant B would be similar to A, but the angles would be oppositeor reversed. That is, if the angle 3 /2" in FIGURE 2 for quadrant Aextends downwardly, the corresponding angle for quadrant B would extendupwardly; and if the 4 /2" angles of quadrant A is to the right at thereflector, then in quadrant B it would be to the left at the reflector.We refer to the direction at the reflector because the plane of the cutcrosses the axis 8 at the focal point.

Two quadrants A are made and two quadrants B; only one quadrant A can becut from a single paraboloid, because of the angles. Although we havespoken of cutting the segments out and then fitting them together toform my composite reflector, the commercial units are punched out of asingle sheet of metal by a die formed to the same shape as it cut asdescribed.

The resultant reflector 1 and lamp 3 are put together with the filament5 of said lamp 3, or the center of said filament, being at the focalpoint with the filament transverse and the reflector axis. However, thelamp can be moved in or out of the reflector, somewhat away from thefocal point, to spread or narrow the beam. FIGURE 4 shows a schematicdiagram of the generally rectangular field to be illuminated by mydevice. The field is divided into four rectangular quandrants A, B, A,B. The beam from the top quadrant A in FIGURE 3 will illuminate thelower quadrant A in FIGURE 4 and vice versa, the beam from each quadrantcrossing the axis 8 of the reflector 1 because of the tipping of thereflector quadrants toward said axis. The same relationship existsbetween the quadrant B on the reflector of FIGURE 3 and on therectangularly illuminated field of FIGURE 4.

The center a, b of beams A, B are approximately along the diagonals 10,11 and about two-thirds of the distance from the center of theilluminated rectangle to the corner. The beams from the four quadrantswill overlap at the center portion of the rectangle, so that a centeringof each beam at the distance given results in most uniform illumination.

In one embodiment of the invention, the original paraboloid was formedfrom a parabola =0.5714y and the open face was about 2.5 inches indiameter. The lamp used was the kind designated in the industry as aDVY.

What I claim is:

1. A lighting unit for producing a generally rectangular beam, said unitcomprising: two quadrants of a paraboloid of revolution, each quadrantbeing bounded by two planes, one plane passing through the focal pointof the paraboloid at a small dihedral angle and the other plane passingthrough said focal point at a small dihedral angle to a plane which isat a dihedral angle of about 90 with said plane through the axis, saidquadrants being set opposite each other on opposite sides of said axisto form two contiguous portions of the surface of a reflector; and twointermediate quadrants, each set between the other two quadrants andjoined therewith to form an integral complete reflector, each of saidintermediate quadrants being quadrants of a paraboloid substantiallyidentical with that of the first two quadrants, but in which theboundary planes are at dihedral angles with the axis plane 4 and theplane at about 90 to it, such that the dihedral angles are the same inmagnitude but opposite in direction to those of the two first-mentionedquadrants.

2. The lighting unit of claim 1, in which the firstmentioned smalldihedral angle is about 3 /2 and the second-mentioned small dihedralangle is about 4 /2.

3. The lighting unit of claim 1, in which each quadrant of the reflectoris set to direct light to a different quadrant of the rectangular fieldto be illuminated.

4. The lighting unit of claim 3, in which each quadrant of the reflectorreflects a beam across the axis of the reflector as a whole.

5. The lighting unit of claim 4, in which the beam from each quadrant iscentered on a point on a diagonal of the rectangular field to beilluminated and about twothirds of the distance from the center of therectangle to the corner along the diagonal.

References Cited UNITED STATES PATENTS 1,417,926 5/1922 Lester 24041.371,663,008 3/1928 Johnson 24041.37 3,132,812 5/1964 Strobel 240103 XR3,331,960 7/1967 Elmer 240-403 NORTON ANSHER, Primary Examiner.

ROBERT P. GREINER, Assistant Examiner.

US. Cl. X.R. 24011.4, 103

